1. Technical Field of the Invention
This invention relates to a method for the manufacture and purification of methyl tertiary butyl ether prepared from tertiary butyl alcohol and methanol. More particularly, this invention relates to a method for removing acidic by-products formed during the reaction of tertiary butyl alcohol with methanol.
Methyl tert-butyl ether is finding increasing use as a blending component in high octane gasoline as the current gasoline additives based on lead and manganese are phased out.
2. Prior Art
In U.S. Pat. No. 4,144,138 (1979) to Rao et al., there is disclosed a method for recovering methyl tertiary butyl ether from etherification reaction effluent by azeotropic distillation to recover methanol-ether azeotrope overhead which is water-washed to give pure ether raffinate, the latter being azeotropically distilled to yield ether-methanol overhead which is recycled to water washing.
Kruse et al. U.S. Pat. No. 5,243,091, entitled "Method for the Manufacture and Recovery of Methyl Tertiary Butyl Ether", discloses a method for the preparation of methyl tertiary butyl ether wherein tertiary butyl alcohol is reacted with methanol to provide a reaction product comprising methyl tertiary butyl ether and by-product isobutylene and wherein the by-product isobutylene is reacted with methanol to provide additional methyl tertiary butyl ether and also a water washing method for the purification of the methyl tertiary butyl ether.
Gupta U.S. Pat. No. 5,292,964 discloses a process for the manufacture of methyl tertiary butyl ether from tertiary butyl alcohol and methanol wherein tertiary butyl alcohol is reacted with methanol in a primary reaction zone to provide a reaction product comprising methyl tertiary butyl ether, unreacted tertiary butyl alcohol, unreacted methanol and water, wherein the reaction product is separated in a distillation zone into a lighter fraction comprising substantially anhydrous methanol and methyl tertiary butyl alcohol and a heavier fraction comprising tertiary butyl alcohol, methanol and water, and wherein the lighter fraction is charged to a finishing reactor wherein the methanol is reacted with isobutylene to form additional methyl tertiary butyl ether.
The preparation of methyl tert-butyl ether from methyl and tert-butyl alcohols is discussed in S. V. Rozhkov et al., Prevrashch Uglevodorodov, Kislotno-Osnovn. Geterogennykh Katal. Tezisy Dokl., Vses. Konf., 1977, 150 (C. A. 92:58165y). Here the TBA and methanol undergo etherification over KU-2 strongly acidic sulfopolystyrene cation-exchangers under mild conditions. This reference contains data on basic parameters of such a process.
In Cassata et al. U.S. Pat. No. 5,395,982, filed Nov. 8, 1993, and entitled "Continuous Isobutylene-Assisted Aqueous Extraction of Methanol from Methyl Tertiary Butyl Ether," a process is disclosed wherein an impure methyl tertiary butyl ether product contaminated with isobutylene, methanol and water is purified by continuous counter-current contact with water and isobutylene in a counter-current contact extraction tower to provide an overhead raffinate comprising isobutylene, methyl tertiary butyl ether and water and an extract comprising methanol, water and a minor amount of methyl tertiary butyl ether, the overhead raffinate being separated in a methyl tertiary butyl ether purification distillation zone into a lighter distillation fraction comprising isobutylene and water and a heavier distillation fraction consisting essentially of methyl tertiary butyl ether, the lighter distillation fraction being decanted to remove water and to provide a distillate isobutylene fraction that is returned to the contact tower.
In copending Peters et al. U.S. patent application Ser. No. 08/299,391, filed Sep. 1, 1994, and entitled "Preparation of Methyl Tertiary Butyl Ether with Recycle" (D#81,148-D1), there is disclosed a process for the manufacture of methyl tertiary butyl ether from tertiary butyl alcohol and methanol and to the purification of a methanol-contaminated methyl tertiary butyl ether intermediate product formed during the process; the intermediate product being purified by counter-current contact with water in an extraction tower, wherein isobutylene is added to the extraction tower to assist in the formation of an extract composed of methyl tertiary butyl ether, isobutylene and water and in the formation of a raffinate comprising methanol, isobutylene, residual methyl tertiary butyl alcohol and water.